1. 1 © Prentice Hall, 2002 Chapter 14: Object-Oriented Data Modeling Modern Database Management 6 th Edition Jeffrey A. Hoffer, Mary B. Prescott, Fred R. McFadden

2. Chapter 14 2 © Prentice Hall, 2002 What is Object Oriented Data Modeling? Centers around objects and classes Involves inheritance Encapsulates both data and behavior Benefits of Object-Oriented Modeling – Ability to tackle challenging problems – Improved communication between users, analysts, designer, and programmers – Increased consistency in analysis and design – Explicit representation of commonality among system components – System robustness – Reusability of analysis, design, and programming results

3. Chapter 14 3 © Prentice Hall, 2002 Figure 14-1 – Phases of object-oriented systems development cycle

4. Chapter 14 4 © Prentice Hall, 2002 OO vs. EER Data Modeling Object Oriented EER ClassEntity type ObjectEntity instance AssociationRelationship Inheritance of attributes Inheritance of behaviorNo representation of behavior Unified Modeling Language (UML) Object-oriented modeling is frequently accomplished using the Unified Modeling Language (UML)

5. Chapter 14 5 © Prentice Hall, 2002 Object An entity that has a well-defined role in the application domain, as well as state, behavior, and identity – Tangible: person, place or thing – Concept or Event: department, performance, marriage, registration – Artifact of the Design Process: user interface, controller, scheduler Objects Objects exhibit BEHAVIOR as well as attributes entities  Different from entities

6. Chapter 14 6 © Prentice Hall, 2002 State, Behavior, Identity State: attribute types and values Behavior: how an object acts and reacts – Behavior is expressed through operations that can be performed on it Identity: every object has a unique identity, even if all of its attribute values are the same

7. Chapter 14 7 © Prentice Hall, 2002 Figure 14-2 – UML class and object diagrams (a) Class diagram showing two classes Class diagram Class diagram shows the static structure of an object-oriented model: object classes, internal structure, relationships.

8. Chapter 14 8 © Prentice Hall, 2002 (b) Object diagram with two instances Object diagram Object diagram shows instances that are compatible with a given class diagram.

9. Chapter 14 9 © Prentice Hall, 2002 Operations A function or service that is provided by all instances of a class Types of operators: – Constructor – Constructor: creates a new instance of a class – Query – Query: accesses the state of an object but does not alter its state – Update – Update: alters the state of an object – Scope – Scope: operation applying to the class instead of an instance behavior Operations implement the object’s behavior

10. Chapter 14 10 © Prentice Hall, 2002 Associations Association Association: – Relationship among object classes Association Role Association Role: – Role of an object in an association – The end of an association where it connects to a class Multiplicity Multiplicity: – How many objects participate in an association. Lower-bound..Upper bound (cardinality).

11. Chapter 14 11 © Prentice Hall, 2002 Figure 14-3 – Association relationships of different degrees Lower-bound – upper-bound Represented as: 0..1, 0..*, 1..1, 1..* Similar to minimum/maximum cardinality rules in EER

12. Chapter 14 12 © Prentice Hall, 2002 Figure 14-4 – Examples of binary association relationships (a) University example Alternative multiplicity representation: specifying the two possible values in a list instead of a range

13. Chapter 14 13 © Prentice Hall, 2002 (b) Customer order example

14. Chapter 14 14 © Prentice Hall, 2002 Figure 14-5 – Object diagram for customer order example

15. Chapter 14 15 © Prentice Hall, 2002 Association Class An association that has attributes or operations of its own or that participates in relationships with other classes Like an associative entity in ER model

16. Chapter 14 16 © Prentice Hall, 2002 Figure 14-6 – Association class and link object (a) Class diagram showing association classes Binary association class with behavior Unary association with only attributes and no behavior

17. Chapter 14 17 © Prentice Hall, 2002 (b) Object diagram showing link objects Association class instances

18. Chapter 14 18 © Prentice Hall, 2002 Figure 14-7 –Ternary relationship with association class

19. Chapter 14 19 © Prentice Hall, 2002 Figure 14-8 – Derived attribute, association, and role / Derived attributes an relationships shown with / in front of the name Derived relationship (from Registers-for and Scheduled-for) Constraint expression for derived attribute Derived attribute

20. Chapter 14 20 © Prentice Hall, 2002 Generalization/Specialization Subclass, superclass – similar to subtype/supertype in EER Common attributes, relationships, AND operations Disjoint vs. Overlapping Complete (total specialization) vs. incomplete (partial specialization) Abstract Class: no direct instances Concrete Class: direct instances

21. Chapter 14 21 © Prentice Hall, 2002 Figure 14-9 – Examples of generalization, inheritance, and constraints (a) Employee superclass with three subclasses Shared attributes and operations An employee can only be one of these subclasses An employee may be none of them. Specialized attributes and operations

22. Chapter 14 22 © Prentice Hall, 2002 (a) Abstract patient class with two concrete subclasses Abstract indicated by italics Dynamic means a patient can change from one subclass to another over time A patient MUST be EXACTLY one of the subtypes

23. Chapter 14 23 © Prentice Hall, 2002 Class-Level Attribute Specifies a value common to an entire class, rather than a specific value for an instance. Represented by underlining “=“ is initial, default value.

24. Chapter 14 24 © Prentice Hall, 2002 Polymorphism Abstract Operation: Defines the form or protocol of the operation, but not its implementation. Method: The implementation of an operation. Polymorphism: The same operation may apply to two or more classes in different ways

25. Chapter 14 25 © Prentice Hall, 2002 Figure 14-11 – Polymorphism, abstract operation, class-scope attribute, and ordering Class-scope attributes – only one value common to all instances of these clases This operation is abstract…it has no method at Student level Methods are defined at subclass level

26. Chapter 14 26 © Prentice Hall, 2002 Overriding Inheritance Overriding: The process of replacing a method inherited from a superclass by a more specific implementation of that method in a subclass. – For Extension: add code. – For Restriction: limit the method. – For Optimization: improve code by exploiting restrictions imposed by the subclass.

27. Chapter 14 27 © Prentice Hall, 2002 Figure 14-12 – Overriding inheritance Restrict job placement

28. Chapter 14 28 © Prentice Hall, 2002 Multiple Inheritance Multiple Classification: An object is an instance of more than one class. Multiple Inheritance: A class inherits features from more than one superclass.

29. Chapter 14 29 © Prentice Hall, 2002 Figure 14-13 Multiple inheritance

30. Chapter 14 30 © Prentice Hall, 2002 Aggregation Aggregation: A part-of relationship between a component object and an aggregate object. Composition: A stronger form of aggregation in which a part object belongs to only one whole object and exists only as part of the whole object. Recursive Aggregation: composition where component object is an instance of the same class as the aggregate object.

31. Chapter 14 31 © Prentice Hall, 2002 Figure 14-14 – Example aggregation

32. Chapter 14 32 © Prentice Hall, 2002 Figure 14-15 – Aggregation and Composition (a) Class diagram (b) Object diagram

33. Chapter 14 33 © Prentice Hall, 2002 Figure 14-16 – Recursive aggregation

34. Chapter 14 34 © Prentice Hall, 2002 Business Rules See chapters 3 and 4 Implicit and explicit constraints on objects – for example: – cardinality constraints on association roles – ordering constraints on association roles Business rules involving two graphical symbols: – labeled dashed arrow from one to the other Business rules involving three or more graphical symbols: – note with dashed lines to each symbol

35. Chapter 14 35 © Prentice Hall, 2002 Figure 14-17 – Representing business rules Three- symbol constraint Two-symbol constraint

36. Chapter 14 36 © Prentice Hall, 2002 Figure 14-18 – Class diagram for Pine Valley Furniture Company